An inkjet apparatus which has been used as a printing apparatus is also used as an apparatus for forming a wiring or a film these days. With such expansion of applications, the development of materials having performance appropriate for each application has been required.
In the development field of, for example, an electroluminescent element or an organic transistor, a light emitting layer, a transport layer, a semiconductor layer, or the like is formed using a wet method such as an inkjet method or a coating method. As a material for forming these layers, a high molecular weight compound is mainly used.
However, when film formation using a low molecular weight compound as well as a high molecular weight compound by a wet method such as an inkjet method becomes easy, more various elements can be manufactured.
Therefore, a technique for manufacturing an element using a low molecular weight compound as well as a high molecular weight compound is under development. For example, Reference 1 discloses a method for forming a thin film with an inkjet method using a low molecular weight compound by providing a step of forming a self-assembled film (Reference 1: Japanese Patent Laid-Open No. 2003-234522).
In addition, Reference 2 discloses that, when a light emitting layer is formed by a coating method using an organic solvent solution in which a high molecular weight light emitting material is dissolved, there is a problem of invasion of a hole injection layer by the organic solvent (Reference 2: Japanese Patent Laid-Open No. 2003-163086). Further, it also discloses a light emitting element provided with a hole injection layer containing an organic solvent insoluble high molecular weight molecule as its main component in order to solve the problem. According to Reference 2, such a hole injection layer is formed by a method in which a film formed by applying a solution containing an initiator is irradiated with a mercury lamp. However, according to such a method, there is the case where the initiator remains in the film as an impurity.